There is increasing interest in developing wideband and/or multiband antenna systems for use in wireless communications, microwave tomography, remote sensing, and other applications. This has led to increased demand for wideband microwave components, such as antennas. Current and upcoming wireless standards are pushing towards high data rates to accommodate, for example, video streaming and real-time online gaming. The next generation wireless standard will provide an increase in the overall channel capacity 1,000 times greater than current capacity, with multi-Giga bits per second expected to be a reality by the year 2020.
Future wireless standards will rely on novel technologies to increase the data rates and provide reliable links. Current fourth generation (4G) and upcoming 5G will rely on multiple antenna systems with multi-standard support. These multiple standards will operate in different frequency bands with enough frequency bandwidth to provide the expected high data throughput. Antenna elements are usually isolated from one another, and thus occupy a large space within a wireless terminal. The concept of connected arrays (CA) was recently introduced for single band coverage and with single arrays.
The use of multiple-input multiple-output (MIMO) technology as well as the use of higher frequency bands beyond those currently used for wireless communications (i.e. above 6 GHz) will be key factors in achieving the throughput increase. The user terminal will be allowed to carry up to 8-antenna elements within current cellular bands below 6 GHz, with a minimum of 4-antenna elements, depending on the device size and application.
Integrating higher frequency band antennas or antenna arrays along with MIMO antenna systems at the lower bands will be a must to satisfy the large increase in the data throughput expected, as bandwidths of at least 500 MHz are required, and these are not available in the lower spectrum bands.
Such integrated antenna systems that support multiple antennas as well as multiple standards with capabilities both less than 6 GHz and above 10 GHz are of extreme importance for upcoming wireless handheld devices to be able to achieve the expected performance of 5G standards.
Due to the use of multiple antennas in MIMO configurations, space becomes an issue, especially for lower frequency bands, as the antenna elements become larger in size. Coming up with novel compact size and highly efficient antennas is very desirable. At higher frequency bands, i.e. higher than 10 GHz, the free space attenuation of the radio signals becomes large, and thus antenna array configurations are preferred to provide higher gains and compensate for such losses.
The concept of connected antenna arrays (CA) was recently introduced for single band coverage and with single array elements. The idea is to forget the gap between the various antenna array elements, and connect them together in a single wire configuration. Then the feeding points are carefully identified to provide the resonance at the band of interest. This concept yields lower isolation between adjacent elements, but provides much larger operating bandwidths when compared to the conventional methods. Thus far, the concept of CA was applied on simple arrays of single bands and single feeding point.
U.S. Pat. No. 9,413,069 to Chieh et al. and U.S. Pat. No. 8,862,073 to Erceg et al. are exemplary of prior art devices.
Chieh et al. discloses a compact, multi-port, multi-band, Wi-Fi antenna system configured for high-isolation and improved performance. The antenna includes four monopole type antennas each having at least two resonances including 2.4 GHz and 5 GHz for use in Wi-Fi applications.
Erceg et al. discloses a configurable antenna structure including a plurality of switches, a plurality of antenna components, and a configuration module. The configuration module is operable to configure the plurality of switches and the plurality of antenna components into a first antenna for receiving a multiple frequency band multiple standard (MFBMS) signal. The configuration module continues processing by identifying a signal component of interest of a plurality of signal components of interest within the MFBMS signal. The configuration module continues processing by configuring the plurality of switches and the plurality of antenna components into a second antenna.
It would be advantageous to have a compact size MIMO antenna system based on connected arrays that supports multi-bands with multiple configurations. The antenna system of the invention can be placed on the periphery of any wireless terminal with minimum interference with other components within the device or even within the same chassis.